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Configuring Serial Devices

The Serial Line configuration lets you set a WAN device to asynchronous or synchronous if the device supports both line disciplines. It also lets you set HDLC or asynchronous parameters for WAN devices. This document describes the Serial Line configuration commands. It includes the following topics:

Displaying the Serial Line Configuration Prompt

Serial Line Commands

Displaying the Serial Line Configuration Prompt

 The Serial Line configuration applies to a physical device. If you have multiple interfaces on one device, it does not matter which Circuit Config <NET-#> prompt for the device you use to get to the Serial Configuration prompt.

Routers that have multiple serial devices display the slot number of the device that you are configuring as part of the prompt. Serial devices that have multiple ports also show the port number of the device as part of the prompt. For example, the following prompt means you are configuring a serial device in slot 2 port 3.

Serial Config <WAN2-3>
To display the Serial Config <WAN> prompt,

1. To see a list of devices, enter list devices at the Config> prompt. To see a list of interfaces, enter list interfaces at the Config> prompt.

2. Enter the network command to display the circuit configuration prompt. The network number is the number of a serial interface. 

Config>network
What is the network number [0]? 1
Circuit Configuration
Circuit Config <NET-1>
3. Enter sl at the Circuit Config <NET-#> prompt. 

Circuit Config <NET-1> sl
Serial Line Configuration

Serial Config <WAN>

Serial Line Commands

Table 1 summarizes the Serial Line commands.

Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available parameters for each command. Enter help for information about using the command line interface.

[C] means the command is available at the Serial Config <WAN> prompt.

There are no monitoring commands for serial devices.

Table 1 Serial Line Commands

Command Function
E1 [C] [M] Displays the E1 configuration or monitoring prompt.

Exit [C] Returns to the previous prompt.

List [C] Lists the configuration of the serial line.

Set [C] Configures the serial device.

T1 [C] [M] Displays the T1 configuration or monitoring prompt.

E1 [C] [M]

Displays the E1 configuration or monistoring prompt. See Configuring Fractional T1/E1 Devices for information on the commands available at this prompt.

Syntax: e1

Example: e1

E1 user configuration

E1 Config <NET-1>

Exit [C]

Returns to the previous prompt.

Syntax: exit

Example: exit

Circuit Config <NET-1>

List [C]

Lists the configuration of the serial line.

Syntax: list

Example: list

Line Discipline:                  Sync
Maximum network layer frame size: 2048
Speed:                            64000
HDLC Data encoding:               NRZ
HDLC Idle State:                  Flag
Transmit delay counter:           0 units
No cable installed

Set [C]

Sets the line discipline to asynchronous or synchronous. On asynchronous lines, you can set async parameters. On synchronous lines you can set HDLC parameters.

Syntax: set

async databits
async frame-size
async parity
async speed
async stopbits
hdlc cable
hdlc clocking
hdlc encoding
hdlc frame-size
hdlc idle
hdlc speed
hdlc transmit-delay
line-discipline

async databits 7 or 8

Sets the number of bits used to transmit each character. The default is 8.

Example: set async databits

Data bits [8]?

async frame-size #-of-bytes

Sets the size of the network layer portion of frames that the serial device transmits and receives. Does not include data-link and MAC-layer headers. Set the frame size so that it is greater than or equal to the largest frame size configured for any of the interfaces that use this device. The range is 576 to 4088, and the default is 2048.

Example: set async frame-size 

Frame size [2048]?

async parity none or even or odd or mark or space

Sets the type of asynchronous transmission error control to use on the data link. The default is none.

Example: set async parity none

async speed 1200 or 2400 or 4800 or 9600 or 19200 or 38400 or 57600 or 115200

Sets the speed of the transmit and receive clocking lines in bits per second. The default is 57600.

For 14.4k modems, set the speed to 57600.

For 28.8k modems, set the speed to 115200.

Note: For GT 250 routers, the maximum asynchronous speed is 57600.

Example: set async speed 

Line speed [57600]?

async stopbits 1 or 2

Sets the number of bits used to end transmission of a character and put the line back into marking state. The default is 1.

Example: set async stopbits

Stop bits [1]?

hdlc cable type

 If the device you are configuring does not detect the cable type to which it is connected, sets the cable type. The options are

Note: If you are using an RS-449 cable, set the cable type to V36.

 Example: set hdlc cable rs-232 dte

hdlc clocking external or internal or mixed

If the device you are configuring detects the cable type to which it is connected, the device also sets the appropriate clocking, and this parameter does not appear.

To connect to a modem or DSU, configure clocking as external. To connect directly to another DTE device, use a DCE cable and set the clocking to internal. If the modem provides the receive clock lines and expects the transmit clock line, use mixed.

For internal and mixed clocking, use the set hdlc speed command to configure a clock speed.

For external clocking, if you want line speed reporting, set the external clock speed using the set hdlc speed command. You can display the line speed using the interface command at the + prompt or using SNMP.

Note: You cannot boot over a GTAM Quad serial device when you configure clocking as mixed.

Example: set hdlc clocking internal

hdlc encoding NRZ or NRZI

Sets the HDLC transmission encoding scheme for this device to either NRZ (Non-Return to Zero) or NRZI (Non-Return to Zero Inverted). The default is NRZ.

Example: set hdlc encoding nrz

hdlc frame-size value

Sets the size of the network layer portion of frames transmitted and received on the data link. Data link and MAC layer headers are not included. The range is 576 to 4088, and the default is 2048.

Example: set hdlc frame-size

Frame Size [2048]?

hdlc idle flag or mark

 Sets the data link idle state to either Flag or Mark. The default is Flag.

Example: set hdlc idle flag

hdlc speed bits per second

If you set hdlc clocking to

For GTAM devices, the range is 0 to 6250000, and the default is 0. For GTS 250 devices, the range is 0 to 6250000, and the default is 0. For all other devices, the range is 0 to 10000000 bps, and the default is 57600.

Example: set hdlc speed 

Clock Speed [64000]?

hdlc transmit-delay

Allows you to insert a delay between the transmission of each frame. Use this command to slow the serial line so that it is compatible with slower devices at the other end.

For GTAM devices, sets the period of time, in microseconds, between the transmission of each frame. The range is 0 to 65535.

For all other devices, sets the number of extra flags between each frame. The range is 0 to 15.

For all platforms, the default is 0, which means the router does not insert a delay between frames.

Example: set hdlc transmit-delay

Transmit Delay Counter [0]?

line-discipline async or sync

Sets the line discipline to synchronous or asynchronous. The default is sync.

Example: set line-discipline async

T1 [C] [M]

Displays the T1 configuration or monistoring prompt. See Configuring Fractional T1/E1 Devices for information on the commands available at this prompt.

Syntax: t1

Example: t1

T1 user configuration

T1 Config <NET-1>

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